The Influence Of Dexmedetomidine On Hemodynamic Of Patients Undergoing Coronary Artery Bypasses Grafting With Thoracic Epidural Anesthesia

BackgroundDexmedetomidine (DEX) is a new highly selective α2adrenergic receptor (α-2AR) agonists, which plays a pharmacological effect through the combination with the α-2R. a-2AR distributes in the adrenergic neurons of the sympathetic nerve endings and the central nervous system. It can inhibit norepinephrine release and reduce the concentration of catecholamines in the blood after stimulation. α-2AR subtypes include alpha2A, a2B, a2C, these receptor subtypes are widely distributed and each plays its unique role. The edative、analgesic effect and the role of anti-sympathetic role of non-selective a2-AR agonist is mediated by a2A receptor subtype, a2C receptor subtypes mediate the anxiolytic effects,and a2B receptor subtype can produce short-term blood pressure response. Dexmedetomidine is a new type of highly selective a2-adrenergic receptor agonist, the affinity of the a2adrenergic receptor is about8times than clonidine, and the titer is about3times than clonidine. Its half life is shorter (approximately2hours), the clinical application is sedative, analgesic and anxiolytic. In addition to as the sedative drugs in ICU, dexmedetomidine is used for clinical anesthesia recently. But the accepted dose is based on the results of human study population of Western Europe and the United States, the experience in Chinese is still shallow, especially in the use of epidural combined with general anesthesia. High thoracic epidural anesthesia (HTEA), administered in addition to general anesthesia, has been extensively investigated because of its potential beneficial effects including perioperative stress response attenuation, cardiac sympathetic nerve blockade, and excellent analgesia. Moreover, HTEA dilates epicardial coronary arteries, partly normalizes the myocardial blood flow in response to sympathetic stimuli, improves left ventricular function, has anti-ischemic properties, reduces postoperative release of cardiac troponin I (cTnI)9and T (cTnT). The use of epidural anesthesia and analgesia techniques in patients undergoing cardiac surgery has gained increasing popularity in recent years. In fact, this technique has been considered to be potentially beneficial because it was thought to attenuate the stress response to surgery, to reduce the sympathetic tone,and to provide improved postoperative analgesia. These effects should result in improved myocardial perfusion and reduced perioperative myocardial ischemia. Moreover, it was previously shown that HTEA could reduce the risk of postoperative pulmonary complications. One of the potential advantages of HTEA, derived from its physiologic features (coronary vasodilation, myocardial oxygen consumption decrease), is a reduction of myocardial ischemia. Loick et al showed that new ST-segment elevation or depression occurred less frequently in the group of patients treated with HTEA. Accordingly, Berendes et al showed a reduction of regional wall motion abnormalities, detected with transesophageal echocardiography, and a reduction of postoperative ischemia in patients treated with HTEA in comparison to a control group treated with general anesthesia. The above effects should improve myocardial perfusion and reduce the incidence of perioperative myocardial infarction.TEA has an inherent risk of cardiovascular depression and arterial vasodilation. The hemodynamic effects of combined TEA and GA increase the risk of severe intraoperative hypotension, which may offset the positive hemodynamic effects of TEA. Severe hypotension is a great risk for some patients, such as coronary heart disease and hypertension. It is extremely important to maintain the hemodynamic stability, especially to prevent the incidence of hypotension during epidural anesthesia. Studies have shown that DEX can reduce the dosage of these drugs by strengthening the collaborative role of other narcotic drugs and sympathetic blockade drugs and maintain hemodynamic stability by inhibiting the stress response which reduces the release of catecholamines. Possible causes include:1. DEX acts in the central, inhibits of sympathetic impulse and results in the central antihypertensive effect, while reducing the intraoperative blood pressure play a role in reducing bleeding. Clear the operative field due to reduced bleeding, thereby reducing the use of narcotic drugs to lower blood pressure, and a corresponding reduction in the use of narcotic drugs.DEX can reduce the plasma cortisol and catecholamine concentrations, reduce the stress response in patients undergoing to reduce blood pressure. Excessive DEX use (1.0-2.5μg/kg) or injection speed too fast can cause high blood pressure, followed by a drop in blood pressure accompanied by tachycardia. The reason of this two-way reaction may be:First, DEX rapidly combined with the blood vessels of a2-receptors after intravenous administration, resulting in peripheral vasoconstriction caused by high blood pressure; then spread to the central nervous system, inhibition of the vasomotor center and plasma norepinephrine adrenaline levels, causing decreased blood pressure. There is evidence that perioperative application of, a2-receptor agonist, can reduce cardiovascular surgery and non-cardiac surgery, patients after myocardial ischemia, myocardial infarction and death incidence.The subject is on the basis of the foreign reference,and to explore the hemodynamic stabilizing effect of DEX during the induction of general anesthesia or epidural anesthesia combined by general anesthesia using international most advanced research tools and technical indicators, vertebraltube block auxiliary in anesthesia and sedation, a series of studies, conduct a comprehensive evaluation of its safety and effectiveness in the clinical application.This would provide great significance in guiding clinical practice.The ultimate goal of medical research is to serve for clinical practice; the results of our research provide a scientific basis to guide the clinical application. The research team conducted a systematic clinical research on the general anesthesia (induction of anesthesia, maintaintion of anesthesia, recovery from anesthesia), spinal anesthesia, some special patients (hypertension, coronary heart disease, neurological surgery, as well as non-artificial airway in patients with, etc.), as well as its application in the spinal canal. We boldly explore and try its safety, efficacy and feasibility in clinical anesthesia which provides reliable information and valuable experience for clinic practice.Methods1DEX as a part of general anesthesia medication, to investigate the hemodynamic stability during the induction of general anesthesia.Seventy-five patients (aged46-72years, weighing59-86kg, ASA II or III, EF≥45%) undergoing myocardial revascularization were randomised into three equal groups. Patients were respectively administered with dexmedetomidine0.8μg/kg (group DS) either sodium chloride (group S1or group S2) before the anesthesia induction. Anesthesia was induced with midazolam0.08mg/kg’and followsufentanil0.5μg/kg (group DS and group S1) or0.8μg/kg(group S2). Tracheal intubation was facilitated with vecuronium0.12mg/kg. Heart rate (HR), arterial pressure (SBP, DBP and MAP) was recorded before and after induction of anaesthesia, immediately after intubation, and1,3, and5minutes after intubation. To evaluate the effect of dexmedetomidine combined with low dose sufentanil on prevention of hypotension pre-endotracheal intubation or tachycardia and hypertension caused by endotracheal intubation.2To explore the feasibility of DEX used for sedation during epidural anesthesia.150female patients scheduled for oophorectomy or/and hysterectomy received epidural anesthesia in routine and were randomly assigned to3groups: dexmedtomidine group(Group Dex)、midazolam group(Group Mid) and Propofol group(Group Pro). Ramsay sedation score and bispectral index values were used to observe the sedative effect of dexmedetomidine and midazolam during surgery. To compare the sedative effect of dexmedetomidine and midazolam in gynecologic surgery under epidural anesthesia. 3To explore the impact of DEX on hemodynamic in patients undergoing thoracic surgery under general anesthesia combined with epidural anesthesia.60patients scheduled to undergo elective thoracotomy for lobotomy, or pneumonectomy,40-70years old, ASA I or Ⅱ level. Patients were randomized into1of2groups. T4-5gap epidural catheter, epidural injection of2%lidocaine test dose (3mL) to exclude catheter into the subarachnoid space after injection of0.125%ropivacaine through the epidural catheter7-12ml, so that the block level of T4in. Patients were randomized to dexmedetomidine given group and control group, respectively, before induction of anesthesia,10min intravenous dextromethorphan the care the pyrimidine1μg/kg or normal saline10ml of intubation were given continuous intravenous infusion dexmedetomidine given0.8μg·kg-1·h-1and the same dose of saline to the chest. Evaluation the hemodynamic effects of DEX in patients with thoracic epidural anesthesia combined with general anesthesia.Results1DEX as a part of general anesthesia medication, to investigate the hemodynamic stability during the induction of general anesthesia.Three groups were comparable with respect to age, sex, body weight, duration of tracheal intubation. Compared with other two groups, HR decreased significantly in group SD at all times. SP, DP and MAP decreased significantly in group S2after the induction of general anesthesia. While HR, SP, DP and MAP increased significantly in group S1immediately after intubation and1minute after intubation, but the increase was less than in other groups. In group S2there was an decrease significantly in arterial pressure5minute after intubation, but the decrease was less than in other groups. More patients were treated due to tachycardia and hypertesion in group S1, and hypotesion in group S2.2To explore the feasibility of DEX used for sedation during epidural anesthesia.Dexmedetomidine produced comparable sedation to midazolam. After dexmedetomidine and midazolam were given, BIS values decreased and Ramsay scale increased correspondingly; BIS values were significantly less with dexmedetomidine than midazolam at Ramsay scores of3,4, and5(P<0.05). Compared with Group Mid, heart rate (HR) of Group D was lower at each time point in the surgery; while mean artery pressure (MAP) was no significant difference. No respiratory depression happened in Dex group.3To explore the impact of DEX on hemodynamic in patients undergoing thoracic surgery under general anesthesia combined with epidural anesthesia.Before the induction of the DEX group, the HR was significantly lower than those in the placebo group; two groups after the induction of SBP decreased, but the DEX group (127±24mm Hg) SBP was significantly higher than the placebo group (90±20mmHg). Despite the application of a vasoconstrictor, the placebo group (96±15mm Hg) systolic blood pressure before intubation was significantly lower than the DEX group (131±15mmHg). After intubation, SBP in the placebo group to150±31mmHg. However, the DEX group, SBP did not change significantly. DEX group after intubation(134±15mm Hg) of SBP in the placebo group no significant differences. A result of induction of the DEX group (-12%±12%) percentage decrease in SBP than in the placebo group (-38%±15%). Intubation caused by DEX group (3%±4%). The SBP percentage increase is lower than the placebo group (70%±34%). Anesthesia was maintained during the DEX group, boost the application of vasoactive drugs was significantly less than the placebo group (P<0.01), heart rate and fentanyl consumption was significantly lower than those in the placebo group (P0.01);Conclusions1DEX as a part of general anesthesia medication, to investigate the hemodynamic stability during the induction of general anesthesia.Dexmedetomidine(0.8μg/kg) combined with sufentanil(0.5μg/kg) during anesthetic induction for patients with coronary artery bypass grafting can suppresses the decreses in blood pressure due to anesthetic induction and also blunts the cardivbascular response to tracheal intrbation.2To explore the feasibility of DEX used for sedation during epidural anesthesia. Dexmedetomidine for sedation in gynecologic surgery under epidural anesthesia is safe and feasible. Compared with midazolam, it not only provides a satisfactory sedation but wakes up easily without inhibiting respiration.3To explore the impact of DEX on hemodynamic in patients undergoing thoracic surgery under general anesthesia combined with epidural anesthesiaDexmedetomidine provides stable hemodynamics in patients under high epidural thoracic anesthesia combined with general anesthesia, reducing the occurrence of hypotension after induction of and the hypertension after double-lumen endotracheal intubation. During the maintenance period of anesthesia DEX reduced occurrence of the epidural anesthesia-induced hypotension, and reduced the application of intraoperative opioids.